JPH05112491A - Production of ethyl acetate - Google Patents

Abstract

PURPOSE:To provide an extremely effective method for efficiently and stably producing industrially useful ethyl acetate in the liquid phase by using a heterogeneous catalyst. CONSTITUTION:Ethylene is reacted with acetic acid in the liquid phase under pressure of the ethylene by using a solid catalyst, having part of protons, possessed by phosphotunstic acid and substituted with cesium metallic cations and insoluble in the reactional phase as a catalyst to produce ethyl acetate. Since the catalyst is a heterogeneous catalyst, having extremely high reactional activity and insoluble in the reactional phase, recovery is facilitated and the method is suitable as an industrial method for production. Furthermore the reactional selectivity is excellent and the catalyst has its life of a long period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing ethyl acetate, which is useful as a raw material for ethyl acetate paints, various chemicals and industrial chemicals and which is consumed in large quantities.

[0002]

2. Description of the Related Art Conventionally, as a method for producing ethyl acetate, which has been widely industrialized, a production method by an esterification reaction of ethanol and acetic acid and a dimerization reaction of acetaldehyde in the presence of a metal alkoxide catalyst are known. ing. Here, in the production method by the esterification reaction, ethanol is used as a raw material in addition to acetic acid, and this ethanol is usually industrially produced from ethylene as a raw material, and is a so-called secondary raw material and expensive in Japan due to national policy. It is a substance. Furthermore, the esterification reaction is an equilibrium reaction, and in order to increase the conversion rate of the reaction, it is necessary to continuously remove by-produced water from the reaction system by some method. This is a problem in terms of raw materials for production, production equipment and utility, and there is room for improvement.

Further, in the dimerization reaction of acetaldehyde (so-called Tishitienko reaction), acetaldehyde which is a raw material is a secondary raw material produced from ethylene.
Further, it is known that this dimerization reaction achieves a high conversion rate and high selectivity in a mild manner. However, the catalyst used for this is usually an alkoxide of a metal such as aluminum, and the formation of acetoaldol as a side reaction of the dimerization reaction and this dehydration reaction are unavoidable, and the metal alkoxide catalyst is formed by the water generated by this dehydration. Easily disassembled. Therefore, there are major problems in terms of raw material and life of the catalyst. Here, as a new method for producing ethyl acetate, a method for producing ethyl acetate using ethylene as a raw material has been actively studied. This production method proceeds as a direct addition reaction of acetic acid to ethylene, and an acid catalyst is used as a catalyst.

For example, a liquid phase catalytic reaction is disclosed in Japanese Patent Laid-Open No. 55-
In Japanese Patent No. 160745, trifluoromethanesulfonic acid is used as a catalyst, in Japanese Patent Publication No. 63-51060, sodium cation-exchanged sodium bentonite is used as a catalyst, and in Japanese Patent Publication No. 56-30334, a heteropoly acid of tungsten soluble in a reaction solution or its compound is used. The catalyst is an acidic metal salt. Among them, when a trifluoromethanesulfonic acid catalyst is used, the reaction results are good, but trifluoromethanesulfonic acid itself is expensive and very unstable. In addition, it is a liquid-phase homogeneous catalyst that exhibits extremely strong acidity and has large corrosion in reactors and the like. Similarly, the heteropoly acid of tungsten and the acidic metal substitution catalyst thereof are liquid phase homogeneous catalysts, and have large corrosion. Furthermore, these liquid phase homogeneous catalysts are easy to separate from the product ethyl acetate, but it is extremely difficult to separate from the high boiling substances among the by-products formed during the reaction, and the recovery of the catalyst is practically impossible. Regeneration is not possible, as a result of which the catalytic activity is impaired and its life is shortened. In addition, a metal cation-exchanged bentonite catalyst requires a large amount of the catalyst and the reaction must be carried out at a high temperature of 250 ° C. in order to increase the reaction yield. In other words, there is a problem that the catalytic activity is low.

[0005]

The object of the present invention is to produce ethyl acetate by a reaction of addition of acetic acid and ethylene in a liquid phase state of acetic acid under a mild condition with a high selectivity and a high conversion rate and to produce a catalyst. It is an object of the present invention to provide a method for producing ethyl acetate which is homogenized and facilitates catalyst separation, and in addition, gradually reduces corrosion and the like of a reactor.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have investigated a processically and reactively effective production method of ethyl acetate,
Focusing on the fact that the addition reaction of acetic acid and ethylene in the liquid phase of acetic acid is an excellent production method, the conventional drawbacks are low catalytic activity, low catalytic activity, and problems of separability of the catalyst. As a result of intensive studies to solve various problems such as reactor corrosion, a liquid phase heterogeneous catalyst was obtained by allowing a catalyst in which part of the protons of phosphotungstic acid was replaced by a cesium cation to exist in the reaction system. The inventors have found that the process proceeds extremely efficiently, the catalyst can be easily separated and recovered, and the catalyst can be stably carried out for a long time, thus completing the method of the present invention.

That is, acetic acid and ethylene are reacted in the liquid phase state of acetic acid in the presence of a heterogeneous solid catalyst in which a part of the protons of phosphotungstic acid is replaced by a cesium metal cation. The production method is represented by the general formula: (M ₁ ) a (P) b (W) c (O) d (H) e (wherein M ₁ represents a metal atom, P represents a phosphorus atom W represents a tungsten atom, and , O is an oxygen atom, H is a hydrogen atom, a is an integer of 0, 1, 2 and b is an integer of 1 or 2, c is a positive integer of 20 or less, and d is 100. Is a positive integer
e is a positive integer of 10 or less. ) A general formula (M ₁ ) a (P) in which a part of hydrogen atoms of phosphotungstic acid (substantially in the form of hydrogen cation) is replaced with cesium metal (substantially cesium cation) b (W) c (O) d (H) ef (C
s) f (where e> f and f is a positive real number) is a phosphotungstic acid-based heteropoly acid. It is also preferable that M ₁ is an element represented by the symbol V, and it is particularly preferable to use tungstophosphoric acid. The method of the present invention will be described in detail below.

The acetic acid used in the method of the present invention does not need to be particularly purified, and acetic acid having a general reagent purity can be used as it is. Also, acetic acid obtained as a usual industrial chemical may be used.

Similarly, the ethylene used in the reaction does not need to be particularly purified, and may be a general reagent purity or one obtained as a general industrial product. Further, impurities such as ethane may be mixed. The catalyst used in the method of the present invention is one in which a part of the protons of phosphotungstic acid is exchanged with a cesium metal cation, and has the general formula (M ₁ ) a (P) b (W) c (O) d (H) ef. (Cs) f (where M ₁ is the element symbol
P is a phosphorus atom, W is a tungsten atom, O is an oxygen atom, H is a hydrogen atom, and Cs is a cesium atom. a is 0, 1 or 2, b is 1, 2 or 3, c is a positive integer of 20 or less, d is a positive integer of 100 or less, e is a positive integer of 10 or less, and f is a positive integer not exceeding e. Is a heteropoly acid in which a part of the protons represented by (C.) is exchanged with Cs + ions. Specifically, dodecatungstophosphoric acid (PW ₁₂ O ₄₀ H ₃ ), dodecathungstophosphoric acid (PMo ₁₂ O ₄₀ H ₃ -fCsf) obtained by Cs ion-exchange of a part of the protons, and one of these tung ten atoms or Heteropolyacids having a structure in which two or more of them are replaced by vanadium atoms are the most easily available heteropolyacids. Here, the substitution rate for substituting the proton of these phosphotungstic acid with the cesium metal cation will be described. The rate of exchange of protons for cesium cations is not particularly limited, but it is preferably 1% to 99% (for example, the value of f in the molecular formula of the above dodecatungstophosphoric acid is 0.03 to 2.97), and 10% to 10%. 90% (f value is 0.3
To 2.7) is more preferable. However, the method of the present invention is not limited to these heteropolyacids.

The method of substituting the proton of the heteropolyacid with the cesium metal cation is not particularly limited in the method of the present invention, and any method can be used as long as the cesium cation and the proton can be exchanged. Examples of a method that can be easily performed include a method of stirring and mixing a solution such as an aqueous solution of heteropolyacid and a solution of a cesium compound. The cesium compound is not particularly limited in the method of the present invention. Examples of easily available ones include cesium acetate, cesium carbonate, cesium hydroxide, etc., and these can be used to easily replace the proton of the heteropolyacid with a cesium cation.

The reaction of acetic acid and ethylene to ethyl acetate in the method of the present invention proceeds as an addition reaction. At that time, the reaction proceeds as a liquid phase heterogeneous catalytic reaction (at least in the state where acetic acid maintains the liquid phase state).

The method of the present invention can be carried out under any conditions of normal pressure, reduced pressure and increased pressure. When it is carried out at a high temperature, pressurization is inevitably carried out in order to maintain the liquid phase state of acetic acid. Pressurized reaction is preferable from the viewpoint of reaction equilibrium.
The reaction system is not particularly limited, but a continuous system, a batch system or a semi-batch system can be used.

In carrying out the method of the present invention, it is possible to add a solvent or an additive which is inert to the catalyst and the reaction reagents (raw materials and products). Specifically, n-
Butane, n-pentane, n-hexane, n-heptane,
Aliphatic saturated hydrocarbons such as n-octane, n-nonane, and n-decane, aromatic hydrocarbons such as benzene, toluene, ethylbenzene, xylene, anisole, cumene, and nitrobenzene, cyclopentane, alkyl-substituted cyclopentanes , Alkoxy-substituted cyclopentanes,
Nitro-substituted cyclopentanes, cyclohexane, alkyl-substituted cyclohexanes, alkoxy-substituted cyclohexanes, nito-substituted cyclohexanes, cycloheptane, alkyl-substituted cycloheptanes, alkoxy-substituted cycloheptanes, nitro-substituted cycloheptanes, cyclooctane, alkyl-substituted cyclohexanes It is also possible to use alicyclic saturated hydrocarbons such as octanes, alkoxy-substituted cyclooctanes and nitro-substituted cyclooctanes, and nitrogen, argon, air, helium and the like as a solvent or a diluent.

The quantitative relationship between acetic acid and ethylene charged when carrying out the reaction in the method of the present invention is not particularly limited. The acetic acid / ethylene amount ratio is in the range of 0.1 to 100 (molar ratio). For example, in order to achieve a high conversion of acetic acid, it is desirable to carry out the ethylene to acetic acid ratio of 1 or more, and in order to achieve a high conversion of ethylene, the molar ratio of acetic acid to ethylene should be 1 or more. It is desirable to do in.

In carrying out the method of the present invention, the amount of catalyst to be added is not particularly limited. For example, in the case of a batch reaction, the amount of the catalyst added is 0.1% by weight based on the acetic acid charged. To 100% by weight, preferably 1 to 50% by weight. If the amount is less than this, the reaction proceeds slowly, and if the amount is more than this, the reaction proceeds sufficiently, but it is hard to say that it is preferable from the economical point of view. However, it goes without saying that the method of the present invention can be carried out outside this range.

When carrying out the method of the present invention, the method of charging the catalyst and the reaction reagent is not particularly limited, and the catalyst, acetic acid, ethylene and the like may be charged at the same time. However, since ethylene is usually a gas, acetic acid and the catalyst are used. The method of press-fitting ethylene after charging is recommended. Further, the catalyst may be suspended and charged in another medium or the like.

The reaction temperature in the method of the present invention is not particularly limited, and it can be carried out in a wide temperature range, but it is preferably in the range of 0 to 400 ° C., more preferably in the range of 0 to 400 ° C. It is recommended to carry out at 50 ° C or higher and 300 ° C or lower. If it is carried out at an excessively low temperature, the reaction rate will be lowered, and if it is carried out at an excessively high temperature, the thermal stability of the reaction agent such as ethylene will be deteriorated, which is not economical. In addition, decomposition of the product occurs (reverse reaction to ethylene and acetic acid), which cannot be effectively performed.

The reaction time depends on the amount of catalyst or the reaction temperature, but when the amount of catalyst is large and the temperature is high, it is extremely short (a few seconds or less), and when the amount of the catalyst is small and the temperature is low, it is long (24 It is about time). After completion of the reaction, the target product can be obtained by a separation operation such as a normal distillation operation. Further, the catalyst can be easily separated from the raw material and the product by filtration or the like.

A specific mode for carrying out the method of the present invention will be described. The method for carrying out the method of the present invention is not particularly limited, but the following methods are mentioned as methods that can be easily carried out. Of course, the method of the present invention is not limited to these methods. (1) A stirrer is attached, and a predetermined amount of catalyst and acetic acid are put into an autoclave together with a diluent such as a solvent if necessary, and then a predetermined amount of ethylene is pressed into the autoclave, followed by heating and stirring reaction. (2) A method in which a predetermined amount of catalyst is placed in a reactor which is previously kept at a predetermined temperature and a predetermined pressure, and ethylene and acetic acid are continuously introduced together with a diluent such as a solvent, if necessary, to carry out the reaction. (3) A method in which a predetermined amount of acetic acid and a catalyst are put in advance and ethylene is continuously flown into a reactor kept at a predetermined temperature at a predetermined rate to carry out the reaction.

[0020]

EXAMPLES The method of the present invention will be described more specifically below with reference to examples. Of course, the method of the present invention is not limited to these examples. (1) Quantification of reaction product After the reaction product is reacted at a predetermined temperature for a predetermined time,
After cooling to room temperature, the reaction solution was quantified by gas chromatography. (2) Partial substitution of proton of phosphotungstic acid with cesium cation While stirring an aqueous solution of a predetermined amount of phosphotungstic acid,
A predetermined amount of an aqueous solution of cesium carbonate or cesium acetate was gradually added to this aqueous solution. A white precipitate was precipitated in the stirring liquid when the addition was started. After the addition of the cesium compound was completed, stirring was continued for another 2 hours. This was dehydrated and dried at 80 ° C. under reduced pressure to obtain a white solid. This was used as the reaction catalyst. Further, this solid was dried at 350 ° C. in an electric furnace and used as a catalyst. (3) Calculation of Substitution Amount of Proton of Phosphotungstic Acid by Cesium Cation Total number of hydrogen atoms of phosphotungstic acid used for substitution (A milligram atom) Total number of cesium atoms of cesium compound used for substitution (B) (B The ratio was calculated by the following formula. Therefore, the substitution amount is an average value. Calculation formula (%) = 100 (B / A) In addition, the yield of ethyl acetate in the examples table was based on the charged acetic acid. Unless otherwise specified, commercially available cesium carbonate was used as the Cs compound used in the preparation of the Cs-substituted phosphotungstic acid used in this example.

Examples 1 to 6 Dodecatungstosilicic acid 3 was prepared by exchanging cesium cations in a predetermined amount in a 200 ml autoclave equipped with a magnetic stirrer and heating and drying at 350 ° C. for 5 hours to completely remove attached water or crystal water. After charging 0.05 g and 60.5 g of commercially available 99.5% acetic acid (Kokusan Kagaku), 0.69 mol of commercially available 99.5% ethylene was slowly injected into acetic acid while being absorbed. The autorev was heated with stirring at 500 rpm and reacted at 180 ° C. for 5 hours. The results are shown in Table 1.

Comparative Examples 1 to 4 The reaction between acetic acid and ethylene was carried out under the same conditions as in Example 1 except that 3.0 g of each of the catalysts listed in Table 2 was used. As shown in Table 1, the yield of ethyl acetate was lower than that of the catalyst of the method of the present invention.

[0023]

[Table 1] ─────────────────────────────────── Cs substitution (%) Acetic acid conversion (%) ) Ethyl acetate yield (%) ─────────────────────────────────── Example 1 15 17.2 16.9 Example 2 30 22.7 22.5 Example 3 50 28.3 28.0 Example 4 70 33.1 32.8 Example 5 83.3 34.6 34.3 Example 6 90 15 .9 15.1 ────────────────────────────────────

[0024]

[Table 2] ─────────────────────────────────── Comparative example Catalyst Acetic acid conversion (%) Ethyl acetate Yield (%) ─────────────────────────────────── 1 Dodecatungstophosphoric acid 2.4 2. 12 Dodecatungstosilicic acid 4.9 4.6 3 H-ZSM5 3.7 3.1 4 Al Bentonite (Al 9.4w%) 2.2 1.3 ────────────── ────────────────────── Al bentonite is bentonite with Al cation exchange. The heteropolyacids used in Comparative Examples 1 and 2 are all amorphous water. .

Example 7 All tests were carried out except that the catalyst was not dried at 350 ° C., and was 3.0 g of 83.3% Cs cation-substituted phosphotungstic acid (containing an average of 4.2 molecules of water per molecule of this heteropolyacid). The reaction between acetic acid and ethylene was carried out under the same conditions as in Examples 1-6. The results were that the acetic acid conversion rate was 35.7% and the ethyl acetate yield was 35.5%.

Examples 8 to 11 The reaction between acetic acid and ethylene was carried out under the same conditions as in Example 5, except that the amounts of ethylene charged were those listed in Table 3. The results are listed in Table 3.

[0027]

[Table 3] ─────────────────────────────────── Example Ethylene charge (mol) Acetic acid conversion rate (%) Ethyl acetate yield (%) ─────────────────────────────────── 8 0.42 26 .7 26.2 9 0.61 32.4 31.9 10 0.80 38.9 38.8 11 1.03 44.2 44.0 ──────────────── ─────────────────────

Examples 12 to 14 The reaction was carried out under the same conditions as in Example 5, except that the reaction time was 2, 3 and 8 hours. As shown in Table 4, the yield of ethyl acetate increased as the reaction time increased.

[0029]

[Table 4] ─────────────────────────────────── Example Reaction time (Hr) Acetic acid conversion rate ( %) Ethyl acetate yield (%) ─────────────────────────────────── 12 2 17.3 16 9.9 13 3 22.7 22.5 14 8 39.2 38.9 ──────────────────────────────── ───

Examples 15 and 16 The reaction was carried out under the same conditions as in Example 5, except that the reaction temperatures were 130 ° C and 150 ° C. The results, as shown in Table 5, showed that lowering the reaction temperature reduced the reaction rate, but ethyl acetate was still produced in good yield.

[0031]

[Table 5] ─────────────────────────────────── Example Reaction temperature (℃) Acetic acid conversion rate ( %) Ethyl acetate yield (%) ─────────────────────────────────── 15 130 13.4.3 14 0.0 16 150 22.7 22.5 ────────────────────────────────────

Example 17 After the reaction was carried out under exactly the same conditions as in Example 5, the liquid was separated and recovered from the autoclave, the remaining solid (catalyst) was left as it was, and acetic acid and ethylene were added thereto. The same amount and the same method were used, and the reaction was repeated again at 180 ° C. for 5 hours. This was repeated 3 times thereafter, and the reaction was repeated 5 times in total. As a result, as shown in Table 6, ethyl acetate was produced in a similar yield each time, and deterioration of the catalyst could not be confirmed.

[0033]

[Table 6] ─────────────────────────────────── Reaction times Acetic acid conversion rate (%) Ethyl acetate yield Rate (%) ─────────────────────────────────── 1 33.4 33.0 2 34.6 34.2 3 33.7 33.6 4 35.1 34.8 5 35.6 35.3 ─────────────────────────── ─────────

Example 18 Acetic acid and ethylene were prepared under the same conditions as in Example 5 except that the catalyst was replaced by 3.0 g of dodecatungstophosphoric acid (Cs substitution rate 83.3%) cation-substituted with cesium acetate. Was carried out. As a result, the conversion rate of acetic acid was 33.9.
%, The yield of ethyl acetate was 33.6%. this is,
The cesium compound used to replace the protons of the heteropolyacid with Cs cations means that cesium acetate can also be used.

[0035]

EFFECT OF THE INVENTION By carrying out the method of the present invention, by a liquid phase reaction, ethyl acetate has a high selectivity and a high production yield and can be easily separated and recovered and reused.
It is possible to provide a method capable of producing a high yield.

Claims (3)

[Claims] 1. In the presence of an insoluble heterogeneous catalyst in which part of protons of phosphotungstic acid is exchanged with cesium cations in a liquid phase containing acetic acid, ethylene and acetic acid are reacted in a liquid state with acetic acid. A method for producing ethyl acetate, comprising: 2. The method of claim 1, wherein the phosphotungstic acid is dodecatungstophosphoric acid. 3. The method according to claim 1, wherein the amount of exchanged protons is 10 to 90% on average of all the amount of protons contained in the phosphotungstic acid.